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Suppose a database schedule S involves transactions T1,..., Tn. Construct the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?

1. Topological order
2. Depth-first order
3. Breadth-first order
4. Ascending order of transaction indices

Correct answer: Topological order

Solution

A topological order of the vertices in a precedence graph ensures that for every directed edge from transaction Ti to Tj, Ti appears before Tj in the ordering. This property is essential for constructing a serial schedule that respects the conflicts represented in the graph, thereby guaranteeing serializability.

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